Comportement thermomécanique d'un béton réfractaire : effets du renforcement par des fibres minérales

Adding fibres in concretes can modify their mechanical behaviour. Changes essentially depend on the geometry and on the composition of introduced fibres (metal, glasses, ceramics. . . ), on their volume fraction, on the requested temperature and on the thermomechanical behaviour of the reinforced material. The concrete is a damageable material with a brittle or quasi-brittle behaviour whose properties in direct tension are the weakest. Main objective of the fibre reinforcement is to improve the tension behaviour. Fibres can delay the damage localization phenomenon, can increase the material deformation capacity, can allow a resumption of load after cracking and can increase the peak stress level. These characteristics are also representative of the case of refractory concretes. However, the temperature plays a major role on their mechanical behaviour and microstructural evolutions. The aim of this study is to obtain a better understanding of the thermomechanical behaviour and of the microstructural evolutions of refractory concretes reinforced with mineral fibres. Thus mechanical tests and microstructure observations have been performed in a wide temperature range. Mechanical tests deal with tension tests and four point bending tests. Main microstructure observations have been done by scanning electron microscopy. Complementary results of mechanical tests and microstructural observations have made possible to interpret the behaviour of the reinforced refractory concretes, particularly in terms of reinforcement mechanisms up to 1200°C.